Soaking-pit furnace



April 30, 1929. F. w. MANKER. I 1,111,273

SQAKING PIT FURNACE Filed July 15, 1925 2 Sheets-Sheet 2 abliou vm Patented Apr. 30, 1929.

UNITED STATES PATENT OFFICE.

FORREST WILLIAM MANKER, OF JACKSON HEIGHTS, NEW YORK, ASSIGNOB TO THE SURFACE COMBUSTION COMPANY, INC., OF TOLEDO, OHIO, A CORPORATION OF NEW YORK.

Application filed July 15,

This invention relates to improvements in furnacesand more particularly to that type of furnace known as soaking pits.

Soaking pit furnaces as formerly built have been of the regenerative type. which require a checker brick construction on both sides of the pit, one for air'and one for gas, together with reversing valves and 'flues for the same. The ports through which the air and fuel gas pass are, therefore, a compromise between discharge and fuel ports and are thus not of a proper size for either function. Furthermore. the gases do not obtain their maximum temperature where most desired namely, in the pit where the steel is to be heated, the maximum temperature not being reached until the gases are about to pass out of the furnace.

This condition occurs because of the inability of the gases to become thoroughly mixed before reaching the discharge or outlet port.

The wear 011 the ports is, therefore, very rapid due to high temperature and is oneof the factors contributing to the high cost ofmaintenance of furnaces of this type.

Regenerative furnaces also require attendants to reverse the flow of gases periodically and requir-e.rebuilding of the checker work every 14 to 18 months. Another disadvantage inherent inregenerative furnaces is the in- :o ability to control the mixture of gas and air in any one pit since the pits are usually operated in groups of four and operated with one reversing unit. This results in slowing up operations when certain pits are charged with cold steel and others with hot steel.

The present invention has among its objects to provide a soaking pit furnace in which individual control may be had for each pit; to provide a construction whichiwill make unnecessary the reversal of gases and the attendant complicated flue construction, reversing valves and so forth; .to provide a pit which may be fired from botl'iI-sides simultaneously; to provide for the preheating ofthe air which is to be mixed with the fuel gas; to provide. asimple means for regulating the'alnount of air which'mixes with the fuel gas; to provide means for recirculating some of the hot products of combustion whereby to reduce the amountof fuel necessary to maintain the desired temperature in' the heating chamber or pit; and to make other improvements in soaking pit furnaces as will more fully appear SOAKING-PI'J. summon.

zleconstruction showing how the same may 1925. Serial so; 43,698.

Fig. 1 is a vertical section through the furnace, parts being in elevation and other parts being broken away to more clearly illustrate the construction;

Fig. 2 is ahorizontal sect-ion through the furnace taken on line 22 of Fig. 1, the view also showing, in plan, an adjacent pit of a 6 series;

Fig. 3 is a vertical transverse section of the furnace on line 3-3 of Fig. 1; and Fig. 4 is a detail view of the fuel-gas nozbe water cooled.

The improved furnace includes a plurality of pits arranged side by side, each pit being aself-contained unit, and similar to the other pits. The drawings have therefore been con fined to the illustration of a'one-pit furnace construction except in Fig. 2 wherein the second pit of a series has been indicated.

In the drawings, the soaking pit is indicated at 10. The bottom of the pit has a suitably supported floor 11 on which the ingots 12 rest. Between the floor proper and the ingots is spread a bed of coke 13. The

top of the pit is closed by a slidable cover 14- to permit the insertion and removal of the ingots. L

In each of two opposite side walls of the pit is provided an expanding throat or combustion chamber 16 which extends from side to side of the pit and has its bottom above the floor of the pit. The fuel mixture of as and air enters the combustion cham er 7 through tubes 18 at the restricted end of the combustion chamber, two such tubes being shown in the present instance. These tubes are preferably of the Venturi type and are made of highly refractorymaterial, prefe-rably carborundum. Mounted in axial alinement with these tubes are the. gas nozzles generally indicated at 20. These nozzles are 100 preferablyv adjustably mounted in'the exterior wall of furnagze, which wall is in spaced relation, to the wall in which the tubes 18' are mounted, whereby there is formed a vertically extending passage 22 between the two 105' walls. This passage communicates with'a REISSUED source of heated air, namely, with a recuperator 24. There are two recuperators for each pit, one for each combustion chamber.

The recuperators are heated by the products of combustion flowing from the pit and.

are of hollow tile construction through the passages 26 of which the hot gases flow continuously in one direction. The air to be heated enters the recuperators from the bottom through suitable passages 28, the air circulating around the tiles in channels or paths 29 provided around the latter and finally entering the passage 22 into which the gas nozzles 20 extend.

The hot gases flow from the pit to the recuperators by way of horizontally extending passages 32 and a connecting vertically ex: tending passage 34. The passages 32 open into the pit slightly above the coke bed 13 thereof and below the floor 33 of the expanding combustion chamber 16. In order that the heat of the burnt gases may be utilized to the maximum they are first diverted through the upper part of the recuperator by a bafile 38 in front of the same and then through the lower part of the recu erator passage 22 leading from the recuperator and from whence they pass to the stack y way of a passage 39 below the bafiie 38.

Extending across the vertically extending in alinement with the horizontally extending passages 32 are hollow tiles through which a suitable tool may be inserted from the outside of the furnace to clean said passages 32.

" The outer end of these tiles will, of course,

be kept closed by suitable plugs when not in use. Dust and the like which accumulates in the bottom of the vertical! passage 34 may be removed through a gate or frangible partition 36 above the baflle 38.

As previously indicated the gas nozzles 20 are adjustable in the outer furnace wall toward and from the Venturi tubes 18. Gas

under high pressure is supplied to the nozzles by pipes 44. The gas in passing into the Venturi tubes 18 will therefore entrain .heated air from the supply passage 22. By adjusting the distance between the point of the nozzle and the Yenturi tube the amount of air entrained by the jet of gas can. be varied to suit conditions. If further adjustment of air and gas is desired the size of the Venturi tube may also be varied by removing the tube and replacing it-by one of the desired size. The discharge opening ofthe nozzle may also be varied if desired. By controlling the amount of air entrained by the gas the character of the flame in the combustion chamber may be readily controlled, that is to say, the flame can be made a reducing or oxidizing flame at will. Ordinarilya reduc ing flame will be desired so as to prevent the formation of scale on the ingots. As already stated, the gas supplied to the nozzles 20 is under high pressure and the temperature of the resulting flames is, therefore, high. Localized heat on the face of the billets opposite the combustion chamber, is, however, prevented because of the reduction of velocity of the burning gases in the expanding combustion chamber 16. The heat istherefore a. soft mellow heat, the flames flowing gently around all sides of the ingots,the flames coming from the two combustion chambers meeting each other at the center of the pit and gradually dropping down between the ingots (ofw'hich four are shown in a pit) and then passing out of the pit through the bottom side passages 32 on their way to the recuperators'and stack.

One of the important features of the invention. is the method of and means for recirculating some of the products of combustion whereby to reduce the amount of fuel needed to maintain the desired temperature in the soaking pit or heating chamber 10. Once the refractory material of which'the pit is made has become thoroughly heated, the temperature of the burned gases passing out of the pit will be relatively high. Instead, therefore, of allowing all of the very hot gases constituting the products of combustion to pass to the recuperator, a certain proportion is returned to the pit or, rather to the combustion'ehamber, there to be reheated by the fresh burning gases entering the pit. Due to the fact that the recirculated gases are already very hot, a comparatively small amount of fuel is needed to raise their temperatures sufiiciently to maintain the desired temperature in the pit. The manner in Which the burned gases are recirculated will now be explained.

The floor 33 of the combustion chamber is pierced by ports 40 which open onto the'lateral passages 32 through which the burned gases pass out of the plt to the recuperator. These ports are located in close proximity to the discharge end of the Venturi tubes 18 and consequently the burning gases passing through said tubes will, inasmuch as they have considerable velocity, induce a flow of a portion of the burned gases into the combustion chamber from the passages 32. Theamount of burned gases flowing into the combustion chamber through the ports 40 may be readily controlled by regulating the effective size of the ports by means of cover tiles 42 resting on the floor 33 of the combustion chamber. The other portion of burned gases is allowed to flow to the recuperator toheat the air which isused to support combustion of the gases coming from the supply nozzle. Another efi'ect of recirculating some of the burned gases in the manner specified is to further reduce the velocity ofthe flames or burning gases coming through the nozzles and thus further mellowingthe flames in 'the pit.

Aspreviously 1ndicated the gas nozzles 20 are preferably water cooled. Cooling may be many decided improvements over soaking pit furnaces of the prior art and more particularly over soaking pit furnaces ofthe regenerative type. By firing the-soaking pits from two. opposite sides at the same time, a more uniform heat is obtained in the pit and consequently all of the ingots in the pit will be equally heated; by entering the combustible mixture at points considerably removed from the pit proper and effecting a reduction of the velocity of the same by allowing them toexpand in a combustion chamber of gradually increasing volume before the gases enter the pit proper, localization of the heat on the face of the ingots facing the combustion chambers is effectually prevented; by recirculating a regulated amount of the products of combustion the quantity of fuel required is reduced to the minimum.

It will also be seen that a very simple and eflicacious method has been devised for'controlling the mixture of air and gas which enters the combustion chamber, it being merely necessary to move the gas nozzles 20 toward or from their respective Venturi tubes 18. The closer the tip of the nozzle is to its tube the less air will be drawn into the tube for mixing with the gas, and conversely, the farther-the tip is from its tube the greater will be the amount of air drawn in by the jet of gas. Furthermore by heating the air in a recuperator through which the products of combustion are continuously passing, not only is the temperature of the air higher but a constantly uniform temperature of the air is obtained. This feature marks a decided improvement in the art and is one of the factors contributing to the high eflicicncy of the furnace.

While the improved furnace has been de-.

scribed with considerable particularity of detail, it is to be understood no limitations are intended except as may be defined in the appended claims.

\Vhat is claimed is: 1.- In a furnace having a heating chamber in the form of a pit, an expanding combustion chamber in each of two opposite side walls of the pit, means at the restricted part of each of said combustion chambers for supplying combustible gases thereto, and means below each of said combustion chambers through which pr'oductsof combustion may 2-. In a furnace having a heating chamber in the form of a pit, an expanding combustion chamber in each of two opposite sides of the pit, means at the restricted part of each ofsaid combustion chambers for supplying combustible gases thereto, means extending below each of said combustion chambers through which products of combustion may pass out ofthe pit, and means for directing some of the products of combustion passing from the last-named means into the combustion chamber.

3. In a furnacehaving a heating chamber in the form of a pit, an expanding combustion chamber in each of two opposite sides of the pit, means at the restricted part of each of said combustion chambers. for supplying combustible gases thereto, means extending below each of said combustion chambers through which products of combustion may pass out of the pit, and means for directing some of the products of combustion passing from the last-named means into the combustion chamber at the restricted portion thereof.

4. In a furance having a heating chamber in the form of a pit. an expanding combustion chamber in each oftwo opposite sides of the pit, means at the restricted part of each of said combustion chambers for supplying combustible gases thereto, means extending below each of said combustion chambers through which products of combustion may pass out'of the pit, and means for clirecting some of the products of combustion passing from the last-named means into the combustion chamber, and means for regulating the flow of the products of combustion into the combustion chamber.

5. In-a furnace having a heating chamber in the form of a pit, an expanding combustion chamber in each of two opposite side which some of the products of" combustion may pass into the combustion chamber after they have left the it.

6. In a furnace iaving a heating chamber in the form of a pit, the combination of a tube through which combustible gases are passed, an expanding combustion chamber in which the gases are expanded before en tering .the pit, a gas nozzle in Ia xial alinement with said tube and adjustable toward and from the latter, and an air supplying conduit betw en said tube and thenozzle.

7. In a fun. ace having a heatingchamber in the form of a pit, an expanding combus tion chamber leading away from the pit a Venturi tube in the restricted part of t e combustion chamber and through which tube combustible gases may be passed, a conduit below the combustion chamber through which products of combustion may pass from the pit, and a port connecting said conduit with the combustion chamber at the restricted part thereof whereby some of the products of combustion may be entered into the combustion chamber.

8. In combination, a chamber to be heated, an expending combustion chamber leading thereto, a tube of highly refractory material in the restricted part of the combustion cham- -ber, means for sup lying highly heated air in front of said tu e, and a gas nozzle adjustably mounted in front of said tube, the amount of air flowing into the tube being controlled by adjustment of the gas nozzle toward and from the tube, the entraining action of the as flowing through the nozzle be- 7 ing the e ective medium for carrying the air through the tube.

9. In a furnace having a soaking pit the combination with said pit, of a recuperator at each of two opposite sides of the pit, a combustion chamber in each of the said two opposite sides, means at the closed end of each of said combustion chambers through which combustible gases may be passed, a passage between the respective recuperators and tubes for conducting heated air from the recuperators to the tubs, a gas nozzle for.

each of the tubes, said nozzles extending into said passages and being adjustably mounted with respect to said tubes whereby the amount of air flowing through said tubes may be controlled by the entraining action of a jet of gas passing through said nozzles, and:

means for leading products of combustion out of the pit for passage through the recupera- .tors, said means comprising passages located below said combustion chambers.

10. In a furnace having a heating chamber,

a combustion chamber opening on the heat ing chamber, a port at the closed end of the combustion chamber through which combustible gases may be entered thereinto,

posite directions acplurality of streams of burning gases, withdrawing the products of combustion from a plurality of diametrically opposite points below the points of introduction 0% the burning gases and injecting some of the withdrawn products of combustion into the burning gases before they enter the it. P In testimony whereof I affix my signature.

FORREST WILLIAM MANKER. 

